Axle box for a railway vehicle

ABSTRACT

An axle box for a railway vehicle including a casing provided with a through-bore extending along a median axis, a journal unit accommodated in the bore, a front cover, and a rear cover. At least one part of the front and rear cylindrical parts of the front and rear covers, respectively, having a threaded exterior surface screwed into a tapped portion of the central bore of the casing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to French Application no. 1903210, filed Mar. 27, 2019, the contents of which is fully incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an axle box for a railway vehicle, in particular to the assembling of a journal unit between a front cover and a rear cover on an axle box.

BACKGROUND OF THE INVENTION

Axle boxes are mounted on a railway vehicle, such as passenger wagons, freight cars and locomotives. Generally, a railway vehicle includes a plurality of bogies. Each bogie comprises a chassis, two (or more) wheel sets and four (or more) axle boxes. Each wheel set comprises an axle supporting two wheels. The axle box is the connecting element between the turning wheel set and the quasi-static chassis.

In a known manner, an axle box for a railway vehicle comprises a casing provided with a through-bore extending along a median axis and a journal unit accommodated in the bore.

The axle box also comprises a front cover having a cylindrical part extending axially in the bore of the casing along the median axis and immobilizing the journal unit in a second axial direction, and an annular flange extending radially outwards from the cylindrical part. This flange is generally provided with a plurality of through-openings, each designed to receive a fastening screw or a bolt associated with a tapped nut, the threaded shank of which interacts with a corresponding tapped hole provided on a front surface of the casing.

The axle box also comprises a rear cover having a function similar to that of the front cover and having a cylindrical part extending axially in the bore of the casing on the median axis and immobilizing the journal unit in a first axial direction, and an annular flange extending radially outwards from the cylindrical part. This flange is generally provided with a plurality of through-openings, each designed to receive a fastening screw or a bolt associated with a tapped nut, the threaded shank of which interacts with a corresponding tapped hole provided in the casing.

With a view to ensuring optimal axial retention of the journal unit in the casing and between the front and rear covers, the cylindrical parts are set such that each comes to bear axially against a lateral wall of an exterior ring of the journal unit. The annular flange of the rear cover also comes to bear axially against the rear surface of the casing to which it is secured. However, given the manufacturing tolerances of the front and rear covers, of the exterior ring of the journal unit and of the casing, it is necessary to make provision for axial clearance between the front surface of the casing and the annular flange of the front cover. Thus, upon assembly, it is ensured that the cylindrical part of the front cover comes to bear axially against the lateral wall of the exterior ring before the annular flange comes to bear axially against the front surface of the casing.

Furthermore, the clamping force required in order to secure the front and rear covers to the casing are great enough for it to be necessary to reinforce both the covers and the casing, particularly by forming radial lugs with a view to increasing the rigidity of the assembly, which involves more complex forms and increased costs in terms of material and manufacture. It may also be necessary to make provision for more robust screws by increasing the grade of screw, which implies a higher cost.

SUMMARY OF THE INVENTION

The present invention aims to remedy these aforementioned drawbacks.

More particularly, the present invention aims to provide an axle box for a railway vehicle that is economical, easy to manufacture and easy to assemble.

The invention relates to an axle box for a railway vehicle comprising a casing provided with a through-bore extending along a median axis, a journal unit accommodated in the bore, a front cover and a rear cover.

The front cover has a front cylindrical part extending axially in the bore of the casing on the median axis and immobilizing the journal unit in a first axial direction, and a front annular flange extending radially outwards and fastened securely to a front surface of the casing.

The rear cover has a rear cylindrical part extending axially in the bore of the casing on the median axis and immobilizing the journal unit in a second axial direction.

According to the invention, at least one part of the front and rear cylindrical parts of the front and rear covers, respectively, comprises a threaded exterior surface screwed into a tapped portion of the central bore of the casing.

According to other advantageous but non-mandatory features of the invention, such an axle box may incorporate the following features, taken alone or together with any technically permitted combination:

The journal unit comprises a stationary exterior ring accommodated in the central bore of the casing and an interior ring in rotation about the central axis, the exterior ring being immobilized axially by the front and rear cylindrical parts of the front and rear covers, respectively.

The journal unit is a bearing with rolling elements, at least one row of rolling elements being arranged radially in a radial space defined between the exterior and interior rings.

The front annular flange of the front cover is provided with a plurality of through-openings, each designed to receive a fastening screw or a bolt associated with a tapped nut, the threaded shank of which interacts with a corresponding tapped hole provided in the casing.

The rear cover comprises a rear annular flange extending radially outwards.

The rear annular flange is fastened securely to a rear surface of the casing.

The rear annular flange of the rear cover is provided with a plurality of through-openings, each designed to receive a fastening screw or a bolt associated with a tapped nut, the threaded shank of which interacts with a corresponding tapped hole provided in the casing.

The rear cylindrical part of the rear cover is formed as a single piece with the rear annular flange.

The rear cylindrical part of the rear cover is distinct from the rear annular flange.

The rear cover comprises the rear cylindrical part alone.

The front cylindrical part of the front cover is formed as a single piece with the front annular flange.

The front cylindrical part of the front cover is distinct from the front annular flange.

The front annular flange comprises an annular groove in part receiving the front cylindrical part.

The cover with a screwed cylindrical part comprises a means for interaction with a tool so that it can be screwed into the casing.

The means for interaction comprises at least one hollowed zone provided on the screwed part.

The hollowed zone is radial.

The hollowed zone is axial.

The cover with the screwed cylindrical part comprises at least one through-opening axially receiving a fastening stud, the fastening stud having its end projecting and being received in a corresponding hollowed zone provided on the casing.

The hollowed zone of the casing receiving the fastening stud is an annular groove open axially towards the screwed cover.

The hollowed zone of the casing receiving the fastening stud is a cylindrical blind hole open axially towards the screwed cover.

The fastening stud has a threaded exterior surface and is screwed into an inside thread provided on an interior surface of the through-opening of the screwed part.

The end of the fastening stud received in the hollowed zone of the casing has a conical form.

The end of the fastening stud has a radial length strictly greater than the radial length of the hollowed zone of the casing in which it is received.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood upon reading the following description which is given solely by way of non-limiting example.

The description is given with reference to the appended drawings, in which:

FIG. 1 is an axial cross-sectional view of an axle box according to a first embodiment of the invention;

FIG. 2 is a rear view of the axle box of FIG. 1;

FIG. 3 is an axial cross-sectional view of a detail of the axle box of FIG. 2;

FIG. 4 is an axial cross-sectional view of an axle box according to a second embodiment of the invention; and

FIG. 5 is an axial cross-sectional view of an axle box according to a third embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 to 3 show an axle box, referenced 1 overall, and parts of the axle box according to a first embodiment of the invention.

The axle box 1 comprises a casing 2, a journal unit 3, a front cover 4 and a rear cover 5.

In this embodiment and the following embodiments, the terms “front” and “rear” are defined relative to the position of the axle box in relation to the bogie on rails. A front part is positioned on an axial end of the axle box towards the exterior of the bogie on the rails. A rear part is positioned on an axial end of the axle box towards the interior of the bogie on rails, which corresponds to the side of the wheel.

The casing 2 is illustrated in FIGS. 1 and 2. The casing 2 comprises a through-bore 6 on a median axis X6 defining an axial passage for an axle (not shown). The casing 2 comprises a front surface 7 on an axial side towards the exterior of the bogie and a rear surface 8 towards the wheels. According to one embodiment (not illustrated), the casing 2 may also be provided with supports provided to receive suspension means, such as helical springs.

The bore 6 comprises a cylindrical central bore portion 6-1 in which the journal unit 3 is accommodated.

The journal unit 3 is of standard type. By way of non-illustrated example, the journal unit may be a bearing assembly with rolling elements, in particular with cylindrical or frustoconical rollers. In FIG. 1, and for the purposes of clarity, only one exterior ring 9 of the journal unit 3 is illustrated. Advantageously, the exterior ring 9 comprises an interior surface 9-1, which can form a bearing race for rolling elements, an exterior surface 9-2 mounted by close adjustment in the central bore portion 6-1, and also a front lateral wall 9-3 and a rear lateral wall 9-4 connecting the interior 9-1 and exterior 9-2 surfaces.

The front cover 4 is mounted securely on the front face 7 of the casing 2 and provides axial retention of the exterior ring 9 of the journal unit 3 in a first axial direction directed towards the exterior of the bogie.

The front cover 4 comprises a front cylindrical part 10. The front cylindrical part 10 comprises a cylindrical exterior surface 10-1 accommodated in a front bore portion 6-2 of the bore 6 of the casing 2. The front cylindrical portion 10 thus forms a means for centring the front cover 4 relative to the casing 2. The front cylindrical portion 10 is also provided with a lateral wall 10-2 bearing axially against the front lateral wall 9-3 of the exterior ring 9 of the journal unit 3. The front cylindrical part 10 thus forms a stop for the exterior ring 9 of the journal unit 3 in a first axial direction directed towards the exterior of the bogie. According to the embodiment illustrated in FIG. 1, the front cylindrical part 10 is open axially towards the front of the bogie. According to an alternative (not shown), the front cylindrical part 10 may be closed.

The front cover 4 also comprises a front annular flange 11 extending radially outwards from the front cylindrical part 10. The front annular flange 11 comprises a lateral wall 11-1 secured to the front surface 7 of the casing 2. This front flange 11 is provided with a plurality of through-openings 11-2, each receiving a fastening screw 12, the threaded shank of which interacts with a corresponding tapped hole provided in the casing 2.

According to the first embodiment of the invention illustrated in FIGS. 1 to 3, the rear cover 5 comprises a rear cylindrical part 13. The rear cylindrical part 13 comprises a cylindrical exterior surface 13-1 accommodated in a rear bore portion 6-3 of the bore 6 of the casing 2. The rear cylindrical part 13 is also provided with a lateral wall 13-2 bearing axially against the rear lateral wall 9-4 of the exterior ring 9 of the journal unit 3. The rear cylindrical part 13 thus forms a stop for the exterior ring 9 of the journal unit 3 in a second axial direction directed towards the interior of the bogie, more precisely towards the wheels. The rear cylindrical part 13 also comprises a bore 13-3 provided in order to be traversed by an axle (not illustrated).

According to the invention, the cylindrical exterior surface 13-1 is threaded and the rear bore portion 6-3 is tapped such that the cylindrical exterior surface 13-1 is screwed into the rear bore portion 6-3. The rear cover 5 formed by the rear cylindrical part 13 is thus screwed to the rear face of the casing 2.

The sole function of this rear cover 5 being to ensure axial retention of the journal unit 3 in the second axial direction, it is sufficient to secure the rear cover 5 to the casing 2 by screwing. Fastening screws are thus dispensed with, thereby generating a saving in terms of material, cost, storage and handling.

According to a particularly advantageous embodiment illustrated in FIG. 2, the rear cover 5 comprises a rear annular flange 14 extending radially towards the exterior from the rear cylindrical part 13 and bearing axially against the rear surface 8 of the casing 2. In a particularly advantageous manner, the rear annular flange 14 comprises four hollowed zones 15 distributed regularly over the circumference. The hollowed zones 15 each extend over a defined angular sector and in a radial direction. The hollowed zones 15 thus each define a cylindrical surface 15-1 and two lateral walls 15-2, 15-3 capable of interacting with a dedicated tool applying a clamping torque on the rear cover 5 and thus screwing it into the casing 2.

In an alternative manner, the rear annular flange 14 may comprise fewer than four or more than four hollowed zones 15. According to another alternative, the hollowed zones may be distributed circumferentially in a non-uniform manner These hollowed zones may also be of different forms. According to an alternative embodiment (not illustrated), the means for interaction with a tool consist in at least one axial opening.

According to a particularly advantageous embodiment illustrated in FIG. 2 and shown in greater detail in FIG. 3, the rear cover 5 comprises four through-openings 16 in an axial direction distributed circumferentially in a regular manner Each opening 16 receives a fastening stud 17. The fastening stud 17 may comprise a screw, the threaded body of which is screwed into an inside thread provided in the bore of a through-opening 16, as illustrated in FIG. 3, or a pin, for example.

The fastening stud 17 has a free end 17-1 projecting via the opening 16 and being received in a corresponding hollowed zone 18 provided on the rear surface 8 of the casing 2. In this embodiment, illustrated in FIG. 2, the hollowed zone 18 comprises an annular groove that is open axially towards the rear cover 5. According to an alternative embodiment, the hollowed zone of the casing receiving the fastening screw may be a cylindrical blind hole open axially towards the screwed part.

In a particularly advantageous manner, the end 17-1 of the fastening stud 17 received in the groove 18 has a conical form so as to facilitate the centring and insertion thereof.

According to another particularly advantageous feature, the end 17-1 of the fastening stud 17 has a radial length that is strictly greater than the radial length of the groove 18 into which it is received. Thus, when a sufficiently great clamping torque is exerted on the fastening stud, the end 17-1 locally deforms the groove 18 of smaller radial dimension so as to prevent any relative rotation between the rear cover 5 and the casing 2.

Alternatively, the rear cover 5 may comprise fewer than four or more than four openings. According to another alternative, the openings may be distributed circumferentially in a non-uniform manner These openings and fastening studs may also be of different forms.

According to another alternative embodiment (not illustrated), the rear cover 5 does not comprise an annular flange and consists solely of the rear cylindrical part 13.

In the first embodiment illustrated in FIGS. 1 to 3, the rear 13 and front 10 cylindrical parts bear axially against the rear 9-4 and front 9-3 lateral walls, respectively, of the exterior ring 9. The front annular flange 11 bears axially against the front surface 7 of the casing 2, whilst axial clearance is provided between the rear annular flange 14 and the rear lateral wall 8 so as to adjust the axial clamping of the exterior ring 9. In effect, the cover 5 is configured such that, upon assembly thereof, the rear cylindrical part 13 is screwed into the casing until it comes to bear axially against the exterior ring 9 before the annular flange 14 comes to bear against the casing 2, thereby leaving axial clearance. Optimal axial retention of the exterior ring 9 is thus guaranteed. In an alternative manner, the rear annular flange 14 may come to bear against the rear lateral wall 8 of the casing 2, whilst the front cover 4 is configured such as to leave an axial clearance remaining between the front lateral wall 7 and the front annular flange 11.

A second embodiment of the invention is illustrated in FIG. 2. The axial box 1 comprises a journal unit of which the exterior ring 9 is shown, a front cover 20 and a rear cover 21.

The rear cover 21 comprises a rear cylindrical part 22 with a cylindrical exterior surface 22-1 accommodated in a rear bore portion 6-3 of a bore 6 of the casing 2. The rear cylindrical part 22 thus forms a means for centring the rear cover 21 relative to the casing 2. The rear cylindrical part 22 is also provided with a lateral wall 22-2 bearing axially against a rear lateral wall 9-4 of the exterior ring 9 of the journal unit. The rear cylindrical part 22 thus forms a stop for the exterior ring 9 in an axial direction directed towards the interior of the bogie, more precisely towards the wheels. The rear cylindrical part 22 also comprises a bore 22-3 provided in order to be traversed by an axle (not illustrated).

The rear cover 21 comprises a rear annular flange 23 extending radially outwards from the rear cylindrical part 22 and with a lateral wall 23-1 bearing axially against a rear surface 8 of the casing 2. This rear flange 23 is provided with a plurality of through-openings 23-2, each receiving a fastening screw 24 or a bolt provided with a tapped screw, the threaded shank of which interacts with a corresponding tapped hole provided in the casing 2. The rear cover 21 is thus integral with the casing 2.

According to this second embodiment of the invention, the rear cover 21 is formed as a single piece with the rear cylindrical part 22 and the annular flange 23.

The front cover 20 comprises a front cylindrical part 25. The front cylindrical part 25 comprises a cylindrical exterior surface 25-1 accommodated in a front bore portion 6-2 of the bore 6 of the casing 2. The front cylindrical part 25 is also provided with a lateral wall 25-2 bearing axially against a front lateral wall 9-3 of the exterior ring 9.

According to the invention, the cylindrical exterior surface 25-1 is threaded and the rear bore portion 6-3 is tapped such that the cylindrical exterior surface 25-1 is screwed into the rear bore portion 6-3. The front cylindrical part 25 thus forms a fixed stop for the exterior ring 9 in an axial direction directed towards the exterior of the bogie.

The front cover 20 also comprises a front annular flange 26 extending radially outwards from the front cylindrical part 25. The front annular flange 26 comprises a lateral wall 26-1 bearing axially against a front surface 7 of the casing 2. This front flange 26 is provided with a plurality of through-openings 26-2, each receiving a fastening screw 28, the threaded shank of which interacts with a corresponding tapped hole provided in the casing 2. The front cover 20 is thus integral with the casing 2.

According to the second embodiment of the invention, the front cylindrical part 25 and the annular flange 26 are elements that are distinct from one another. The annular flange 26 comprises an annular groove 27 in part receiving the front cylindrical part 25.

In the second embodiment illustrated in FIG. 4, the rear 22 and front 25 cylindrical parts bear axially against the rear 9-4 and front 9-3 lateral walls, respective, of the exterior ring 9. The front annular flange 26 bears axially against the front surface 7 of the casing 2, whilst the rear annular flange 23 also bears axially against the rear lateral wall 8. Axial adjustment of the assembly is achieved by means of the annular groove 27 configured such that axial clearance remains between the back wall of the annular groove 27 and the cylindrical part 25. At the time of assembly, the rear cover 21 is fastened to the casing 2, the rear cylindrical part 22 bearing axially against the exterior ring 9, then the front cover 20 is assembled. First, the front cylindrical part 25 is screwed into the casing 2 until it comes to bear axially against the exterior ring 9. Second, the annular flange 26 is mounted on the casing such that the front cylindrical part 25 is in part accommodated in the annular groove 27. The annular flange 26 comes to bear axially against the front lateral wall 7 of the casing, an axial clearance remaining between the front cylindrical part 25 and the back wall of the annular groove 27. The annular flange 26 is, lastly, secured to the casing 2.

A third embodiment is illustrated in FIG. 3. The axle box 1 comprises a journal unit of which the exterior ring 9 is shown, the front cover 20 similar to that described for the second embodiment and including a front cylindrical part 25 and an annular flange 26 that are distinct, and a rear cover 5 similar to that described for the first embodiment and including a rear cylindrical part 13 and an annular flange.

The front 25 and rear 13 cylindrical parts of the front 20 and rear 5 covers, respectively, are both screwed into the casing 2.

Moreover, the technical features of the various embodiments may, in their entirety or only in the case of certain of them, be combined together. Thus, the axle box may be adapted in terms of cost, performance and implementation simplicity. 

1. An axle box for a railway vehicle comprising: a casing provided with a through-bore extending along a median axis, a journal unit accommodated in the bore, a front cover having a front cylindrical part extending axially in the bore of the casing on the median axis and immobilizing the journal unit in a first axial direction, and a front annular flange extending radially outwards and fastened securely to a front surface of the casing, and a rear cover having a rear cylindrical part extending axially in the bore of the casing on the median axis and immobilizing the journal unit in a second axial direction, wherein at least one part of the front and rear cylindrical parts of the front and rear covers, respectively, comprises a threaded exterior surface screwed into a tapped portion of the central bore of the casing.
 2. The axle box according to claim 1, wherein the rear cover comprises a rear annular flange distinct from the rear cylindrical part.
 3. The axle box according to claim 1, wherein the front cylindrical part of the front cover is distinct from the front annular flange.
 4. The axle box according to claim 3, wherein the front annular flange comprises an annular groove that receives the front cylindrical part.
 5. The axle box according to claim 1, wherein the cover with a screwed cylindrical part comprises a means for interaction with a tool so that it can be screwed into the casing.
 6. The axle box according to claim 5, wherein the means for interaction comprises at least one hollowed zone provided on the screwed part.
 7. The axle box according to claim 1, wherein the cover with the screwed cylindrical part comprises at least one through-opening axially receiving a fastening stud, the fastening stud having its end projecting and being received in a corresponding hollowed zone provided on the casing.
 8. The axle box according to claim 7, wherein the fastening stud has a threaded exterior surface and is screwed into an inside thread provided on an interior surface of the through-opening of the screwed part.
 9. The axle box according to claim 7, wherein the end of the fastening stud received in the hollowed zone of the casing has a conical form.
 10. The axle box according to claim 7, wherein the end of the fastening stud has a radial length strictly greater than the radial length of the hollowed zone of the casing in which it is received. 